The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
The present invention is related in general to equipment for servicing subterranean wells. Particularly, the invention relates to a cementing head that is intended to drop a combination of darts, balls, bombs and canisters in order to activate downhole equipment, launch cementing plugs, deliver chemical products, or the like.
Tools currently available on the market for downhole services implement a modular design with darts that are preloaded in baskets within the modules. The modules are connected to one another using clamps. The darts are held in place mechanically and released by removing the mechanical obstruction and redirecting the flow of the pumped fluid (hereinafter called “process fluid”) through the dart basket. The darts are then pumped through the tool by the fluid. The first dart to be launched is placed in the lowest module, with subsequent darts passing through the baskets vacated by the earlier darts.
Darts in prior designs are launched by blocking the bypass flow of the process fluid and forcing the fluid through the dart chamber. The dart forms an initial seal when placed into the basket. When fluid enters the dart chamber, pressure builds and breaks the seal, forcing the dart out of the basket, through the tool and into the main process-fluid stream.
Some prior art designs consist of modules such as those described in U.S. Pat. Nos. 4,624,312 and 5,890,537. The darts are loaded from the topmost module, through the swivel if necessary, and pushed down to their respective baskets with a long rod. The modules have valves that are used to select between the dart and the bypass flow. The valve itself serves as the mechanical obstruction that prevents the dart from prematurely launching. When the valve is turned, it simultaneously opens a passage for the dart while closing the passage of the bypass flow.
Another portion of the module is used to launch balls that flow down the well and seat within plugs. Once seated, the balls block the flow of process fluid through the plug, and the resulting pumping-pressure increase causes shear pins to rupture, releasing the plug from its seat. The ball launching portion of the module adds significant length to the cement head.
It remains desirable to provide improvements in wellsite surface equipment in efficiency, flexibility, and reliability.